Thiobisphenol derivatives, such as 2,2'-bis(4-substituted phenol)sulfides, have been recognized as useful in such applications as light stabilizers, polyolefin modifiers, lubricant additives, or intermediates for such products, as shown by UK Pat. No. 2,031,422. Certain tetrahydroxydiphenylsulfides can be prepared by reacting resorcinol and sulfur dichloride in ether as taught by Japanese Pat. No. 7785,129. Experience has shown, however, that when certain bisphenols, such as bisphenol-A or phenols of the formula ##STR1## are reacted with sulfur dichloride in the presence of an organic solvent, oligomeric phenylsulfides can be formed in favor of the desired tetrahydroxydiphenylsulfide, where R is a C(.sub.1-20) divalent organo radical selected from the class consisting of C.sub.(1-8) alkylene radicals, C.sub.(6-14) arylene radicals or substituted C.sub.(6-14) arylene radicals, --O--, --S--, ##STR2## --OR.sup.4 O--, --SR.sup.4 S-- and --CyH.sub.2 y radicals, where y is an integer equal to 1 to 5 inclusive, R.sup.1 and R.sup.2 are members selected from the class consisting of C.sub.(1-8) alkyl radicals, C.sub.(1-8)) alkoxy radicals, C.sub.(6-13) aryloxy radicals, and R.sup.3 S-- radicals, R.sup.3 is a C.sub.(1-13) monovalent hydrocarbon radical, R.sup.4 is a C.sub.(6-14) arylene radical, a is a whole number equal to 0-3 inclusive and b is a whole number equal to 0-4 inclusive.
The present invention is based on my discovery that optimum yields of tetrahydroxydiphenylsulfide of the formula ##STR3## where R, R.sup.1, and R.sup.2, a and b are as prevously defined, can be formed by effecting reaction between at least five moles of bisphenol of Formula 1, per mole of sulfur dichloride, in the presence of Lewis acid catalyst and an inert organic solvent.